1. Field of the Invention
The claimed invention relates to an image forming apparatus for forming an image by using a transparent toner, and an image processing apparatus for processing image data that is to be transmitted to the image forming apparatus.
2. Description of the Related Art
In a conventional electrophotographic image forming apparatus, a toner image is formed and fixed on a recording material with a chromatic toner (a yellow toner, a magenta toner, a cyan toner, and a black toner) to output a print product. An image to be formed on the recording material is designated by a user. In an output image, regions (hair in a portrait image) using a large amount of toner and regions (skin color or the white of the eye in a portrait image) rarely using a toner are often mixed.
In an image forming apparatus for fixing a toner to a recording material, the glossiness of an image after fixing can be changed according to an amount of toner. This may be because some of the fixed toner influences the surface property of a recording material after the toner is fixed. Accordingly, when an image designated by a user is output onto a recording material, an unintended glossiness difference (uneven gloss) corresponding to the unevenness in an amount of chromatic toner may be generated on the recording material.
However, if the amount of chromatic toner is changed to suppress uneven gloss, a color tone may become different from that of an image to be originally output, which is undesirable.
Therefore, some image forming apparatuses can use a transparent toner, which does not contain a color material such as a pigment, to adjust glossiness after fixing. The transparent toner is also used to set up a measure for security, in addition to suppressing an intended glossiness difference caused by a toner step (convexo-concavity) generated by the chromatic toner. More specifically, Japanese Patent Application Laid-Open No. 2004-191626 discusses a method of intentionally forming a transparent toner image on a portion of a recording material and forming a mark (hereinafter, referred to as ‘gloss mark’) which can be recognized visually due to a glossiness difference.
However, when a gloss mark is output by using a transparent toner, it becomes difficult to visually recognize the gloss mark if the glossiness of a portion to which the transparent toner is fixed and that of a peripheral portion thereof become incidentally substantially the same. More specifically, even when the glossiness of a portion of a recording medium is intentionally adjusted by using a transparent toner, it becomes difficult to visually recognize an edge (contour) of the gloss mark at a point where the glossiness of a region where the gloss mark is to be formed and the glossiness of a peripheral region thereof are incidentally substantially the same.
More specifically, the glossiness of a portion (white background portion) where a chromatic toner is not fixed to a recording material becomes intrinsic glossiness of the recording material itself. Accordingly, even when a gloss mark is formed at a white background portion, it becomes difficult to visually recognize the gloss mark if the glossiness of a region to which a transparent toner is fixed is substantially the same as the intrinsic glossiness of the recording material.
In addition, images are often formed with a chromatic toner on a recording material on which a gloss mark is formed, and the gloss mark may be formed to overlap the image formed with the chromatic toner. In this case, it becomes difficult to visually recognize the gloss mark if the glossiness of a region to which the transparent toner is fixed is substantially the same as the glossiness of a region to which the chromatic toner is fixed.
If a transparent toner is formed in a region where a gloss mark is to be formed such that the glossiness of the entire gloss mark region becomes substantially the same, it is difficult to visually recognize an edge (contour) of the gloss mark when the glossiness of the gloss mark incidentally coincides with the glossiness of a peripheral portion thereof.